The present invention relates to a change direction planetary gearing, and more particularly to a change direction planetary gearing for use in a continuously variable transmission.
U.S. Pat. No. 4,735,113, Yamamuro et al., issued on Apr. 5, 1988, discloses a continuously variable transmission. According to this known continuously variable transmission, a forward reverse change-over mechanism or a change direction planetary gearing is disposed between a hydrokinetic unit and a continuously variable ratio change unit. The hydrokinetic unit is in the form of a fluid coupling including a pump impeller and a turbine runner rotatable with a turbine shaft, while the continuously variable ratio change unit includes a driver pulley mounted to a driver shaft, a follower pulley mounted to a follower shaft, and a power transmission endless member (V-belt) interconnecting the two pulleys. The turbine shaft is coaxially aligned with the driver shaft. The turbine and driver shafts are regarded as input and output shafts, respectively, of the change direction planetary gearing. The change direction planetary gearing comprises a reverse brake, a forward clutch and a planetary gear set. The input shaft is rotatable with a sun gear. The planetary gear set includes, in addition to the sun gear, a pinion carrier connected to the output shaft, and a ring gear. The pinion carrier rotatably carries a plurality pairs of intermeshed pinions, each pair meshing and disposed between the sun and ring gears. The forward clutch includes a clutch drum connected to the input shaft, a cylindrical portion integral with a hub connected to the pinion carrier, and interleaved driver and driven frictional plates connected between the clutch drum and cylindrical portion. The reverse brake includes a cylindrical portion rotatable with the ring gear and interleaved driver and driven frictional plates connected between this cylindrical portion and a stationary casing. For forward drive, the forward clutch is engaged with the reverse brake released. Engagement of the forward clutch causes the pinion carrier to rotate with the sun gear, causing the output shaft to rotate with the input shaft in the same forward direction. For reverse drive, the forward clutch is disengaged and the reverse brake is applied. The ring is anchored and thus held stationary with respect to the casing. Thus, rotation of the sun gear in the forward direction causes the pinion carrier and thus the output shaft to rotate in the opposite or reverse direction. In this mode of operation, the clutch drum engaging the driver frictional plate rotates in the forward direction, while the cylindrical portion engaging the mating driven frictional plates rotates in the reverse direction. According to this known change direction planetary gearing, a skilled labour is required to complete assembly of the reverse brake since the interleaved frictional plates of the brake are disposed deeply inside the casing and behind the clutch drum.
An object of the present invention is to improve a planetary gearing of the above kind such that no skilled labour is required in mounting the component parts within the casing.